The project seeks to develop an in vitro technique for maintaining human red blood cells in culture over periods of several weeks. This system will be used to study physiological regulation of cellular volume and cation movements. Fluxes of Na and K as well as cell ion contents of these cations will be periodically monitored during the course of the in vitro incubation of red cells under normal and abnormal physiologic conditions. These data will be combined with a theoretical model of volume regulation to facilitate analysis and prediction.